An apparatus measuring density of media comprises a single section of conduit under flexural vibrations in two lateral directions at two different natural frequencies or two sections of conduit under flexural vibrations at two different natural frequencies, wherein the density of the media moving through the conduit is determined from a combination of the two different natural frequencies, in which combination the effect of the viscosity of the media on the natural frequencies is eliminated and, consequently, the density of the media is determined accurately without errors introduced by the effect of the viscosity.
There are many instances in industrial processes and controls handling the flow fluids wherein the density of the moving fluid has to be measured accurately. One particular application of density measurement is to determine the mass flow rate of a fluid medium as a product of the fluid density measured by a density meter and a volume flow rate of the fluid measured by a volumetric flowmeter. There are mass flowmeters available at the present time such as the Coriolis force or convective inertia force mass flowmeters and thermal probe mass flowmeters. These types of mass flowmeters work poorly in measuring flows of highly viscous fluids due to the error in the data acquisition yielding the mass flow rate arising from the effect of the viscosity of the fluid, while they function excellently in the mass flow measurement of low viscosity fluids. One of the more promising approaches to measurement of the mass flow rate is to employ a combination of an accurate density meter and a reliable positive displacement volumetric flowmeter, which combination is particularly effective in measuring mass flow rates of highly viscous fluids or mixtures of gaseous and fluid medium.